1. Technical Field of the Invention
Implementations consistent with the principles of the invention generally relate to the field of display devices, more specifically to color control of display devices such as display panels.
2. Background of Related Art
Liquid crystal displays (“LCDs”) are display devices often used in computers, televisions, and multimedia monitors. In such displays, much like cathode ray tube (“CRT”) displays, an individual picture element (or “pixel”) that appears to a viewer to be white is actually composed of red, green and blue (“RGB”) primary color components. When each primary color component of the pixel is excited simultaneously and with the appropriate energy, white (or substantially white) can be perceived by the viewer at the pixel screen position. To produce different apparent colors at the same pixel location, the intensity to which the red, green and blue primary components are driven is altered in well known fashions. The separate red, green and blue data that corresponds to the color intensities of a particular pixel is called the pixel's RGB color data (and is sometimes called gray scale data in the case where the red, blue, and green components are constrained to be nearly equal). The degree to which different colors can be achieved within a pixel is referred to as gray scale resolution. Gray scale resolution is directly related to the amount of different intensities, or shades, to which each red, green and blue point can be driven.
The native color temperature of a display device may be observed by having the device display a gray-scale ramp, which results from presenting inputs with equal R, G, and B components which increase in intensity, in unison, from minimum to maximum value while proceeding from left to right across the display screen. Standard measurement apparatus will then report the Correlated Color Temperature (“CCT”), which may not be the same at all points of the ramp. In order to secure a constant, and user-specified, CCT, each of the three input channels may be mapped by use of color control tables, as described herein. It may be noted that, after mapping, the R, G, B triplets will no longer be necessarily equal, and generally only one of the three will reach its former maximum value at the top of the intensity ramp: B, for example, to give the white a blueish cast; R for a reddish cast.
The white balance adjustment for a display is important because many users want the ability to alter the display's color temperature for a variety of different reasons. For instance, the color temperature might be varied based on a viewer's personal taste. In other situations, color temperature adjustment may be needed to compensate for manufacturing variations in the display. Color critical applications such as pre-press soft proofing, desktop publishing, graphics design, medical imaging, digital photography, and video editing require white balance values and gamma values of different displays to be matched so as to accurately view and exchange images with confidence. Color temperature tracking (sometimes also called gray scale tracking) relates to the ability of a display to maintain the same color temperature as the intensity of light changes.
A gamma characteristic is a power-law nonlinear relationship that approximates the relationship between the encoded luminance in a display system and the actual desired image brightness. With this nonlinear relationship, equal steps in encoded luminance correspond to subjectively approximately equal steps in brightness. Display systems that require a linear relationship between these quantities use gamma correction techniques, as skilled artisans recognize.
It is desirable to address the limitations in the art.